The Buzz: Low-Fat vs. Low-Carb Diets for Weight Loss

What’s the buzz?
Choosing whole foods instead of focusing on numbers could be your ticket to weight loss, says new study

What does the science say?
Last month a study published in the Journal of the American Medical Association (JAMA) finally put to rest the debate about whether a low-fat or low-carbohydrate diet is better for weight loss. (At least for the moment.) The verdict? Neither. Or both, depending on how you want to look at it. In a fad diet–obsessed world, this might be a hard pill (or, ahem, diet) to swallow, but you might want to stop counting grams of fat or carbs — or calories, for that matter.

Sounds glorious, right? But before you decide to eat all the things, know that if you’re interested in weight loss, this doesn’t mean you can stop paying attention entirely to what you eat.

Here’s how the study was conducted: Researchers followed 600+ overweight or obese adults for 12 months, tracking their weight, diet, and lifestyle habits. Participants attended regular meetings with a dietitian that focused on how to follow a whole foods–based diet (and avoid processed foods), with either a low-fat or a low-carb focus. Participants were not given specific calorie goals, but instead were told for the first two months of the study to eat only 20 grams of fat or 20 grams of carbohydrate per day, respectively. After two months they were encouraged to keep following either low-fat or low-carb eating patterns, but they were not given specific targets.

Both groups lost similar amounts of weight, an average of 11-13 pounds in a year, though some people lost significantly more while others gained weight —suggesting that both diets can work but neither is a magic bullet for weight loss. This was even true for those believed to be genetically more likely to thrive on the diet they were randomly assigned to, contradicting the idea that dieting based on our DNA may be the way of the future. Both groups also saw improvement in certain biomarkers for chronic disease risk.

Some news reports of this study misinterpreted the findings to suggest that calories don’t play a role, but a peek at the data suggests otherwise (here’s how to identify reliable information!). It’s not that calories don’t count, but more that counting them becomes less important when following a primarily whole-foods diet. Both groups ate about 700 calories less per day during the first two months of the study and averaged a 500-600 calorie daily reduction from baseline over the remaining 10 months. It’s thought that the combination of regular nutrition coaching and the emphasis on choosing whole foods, which are often naturally lower in calories and can be more filling than processed foods, led to the natural calorie reduction.  Of note, calorie intake was trending upward towards the end of the 12 months, so we don’t know if and how long the participants were able maintain that deficit or if weight loss was maintained after the 12 months.

What’s the takeaway?
Whether your trying to lose weight or improve your health, emphasize whole foods rather than specific macronutrients such as fat or carbohydrates. While a calorie deficit still matters for weight loss, choosing whole foods that are filled with fiber, protein, and healthy fats — all of which promote a feeling of fullness — may help people naturally cut calories without having to count them. That makes focusing on a whole foods diet a more effective and easier approach to maintain than counting calories.

Read a detailed breakdown of the findings here.